What did workers find was necessary in order to gain leverage in negotiating with employers?

The creation of trade unions.

Explanation:

A trade union is an organization of workers that unite in order to better defend their rights and bargain with their employers. In the early days of capitalism, labor conditions for workers were extremely poor: they worked long hours, earned low wages, and had no labor rights. Workers who complained or try to get better conditions were more often than not fired and replaced, when not subject of reprisals. Workers came to understand that acting indepently they had no leverage, and thus working conditions wouldn't change unless they acted together as a single front. Following the motto "united we stand, divided we fall", workers organized into labor unions, which act as representatives to workers in negotiations with their employers. Unions grew in size, and now range from single workplace unions, to national and even international trade unions.

not  

cuba  

russia  

iraq  

el salvador  

explanation:

known as the land of volcanoes, el salvador has visit seismic tremors and volcanic movement. it is the main nation in central america that does not have a coastline on the caribbean sea. about portion of all salvadorans live in the wide open. they are poor and don't have power or running water in their homes. in 1525, pedro de alvarado, a lieutenant of cortés's, vanquished el salvador. el salvador, with alternate nations of central america, pronounced its freedom from spain on sept. 15, 1821, and was a piece of a league of central american states until the point when that association broke up in 1838.